Qualification for compressed dry air

Our CDA is used for 1) instrument air for pneumatic valve and 2) process air for oxygen source for bioreactor, pressurizing in vessel and for drying purpose.
The specification of CDA refers to ISO Standards for Compressed Air, ISO-8573 Class 1.4.3.
All points of use will be monitoring for pressure as instrument air.
The point of use for process air will be tested as following:

  1. Oil < 1 mg/m3
  2. particle < 0.1 mg/m3
  3. dew point < 3 deg.C (only test at point of use: sterile autoclave)

microbial limit < 1 CFU/m3 this test will be performed with qualification of process equipment and/or process validation (CDA will be filtered at terminal equipment for all process air).

Question is do we need to perform microbial limit test for instrument air? Should we concern about microbial from CDA that will effect to microbial limit in cleanroom?

Thanks in advance


You should make a Risk assesment what is in contact with compressed dry air. If it is product then your CDA must meet requirement for material in contact with product. If it is not with contact , but it is in some class grade area then air must meet requirements for appropriate class of air.

So I can conclude that microbial limit test is not required for instrument air.


yes i agree, that CDA can direct affect the area count of micro and indirectly affect the product quality both microbially and the humidity also can have the chances to vary

thank you for your answer.

I’ve got some idea. CDA specification should be considered for cleanroom grade A/B.
Does anyone has recommended class of CDA for cleanroom grade A/B?


Hi Sunyaa

I do not know your policy for testing your utilities, but it seem you have 1 CDA grid.

it is correct that for non-product contact usage you do not need to test for microbiology.
Yet, what is your routine sampling of your CDA? Your strategy?
Is it that every so often you sample some of all user points?
What do you do then with your user points that are process points (as such product contact)…
As far as i can conclude from our initiial message, you only test it at the equipment validation level. No routine checks?

What I suggest is that you go check with engineering the possibilities to split the grid in pharma-CDA and CDA. So you branch of near the compressor install filters and construct a pharma CDA that goes to all process users and grade A/ B clean rooms.